TW201212721A - Light emitting diode driving apparatus - Google Patents

Abstract

A light emitting diode (LED) driving apparatus is provided and which includes a power converting circuit for receiving and converting an input power so as to generate a DC voltage to simultaneously drive a plurality of LED strings arranged in parallel; and a plurality of current regulation chips each having a single regulation channel and respectively corresponding to the LED strings, wherein the ith current regulation chip is only used for responsibly regulating a current following through the ith LED string, where i is a positive integer.

Description

201212721 jHjj〇iwf.doc/I VI. Description of the invention: [Technical field to which the present invention pertains] The present invention relates to a light-emitting diode driving device, and more particularly to an expandable and current balancing (current) Balance)/current matching characteristics of the LED driver. [Prior Art] In recent years, with the rapid development of semiconductor technology, portable electronic products and flat panel display products have also arisen. Among the many types of flat panel displays, liquid crystal displays (LCDs) have become the mainstream of display products based on their low voltage operation, no radiation scattering, light weight and small size. In general, since the liquid crystal display panel itself does not have self-illuminating characteristics, it is necessary to place a backlight module under the liquid crystal display panel to provide a (back) light source required for the liquid crystal display panel. The conventional backlight modules can be roughly divided into two types, one is a backlight module composed of a cold cathode fluorescent lamp (CCFL) and the other is a light emitting diode (LED). A backlight module is formed. Among them, since the light-emitting diode backlight module can increase the color gamut of the liquid crystal display, most of the panel manufacturers today replace the cold cathode tube backlight module with a light-emitting diode backlight module. The light-emitting diode backlight module has multiple sets of two light-emitting lights juxtaposed

201212721 ^njjotwi.Joc/I A polar body string, and each light-emitting diode string is composed of a plurality of light-emitting diodes connected in series. In practice, most of the DC-DC converters use a DC-DC converter to convert the input power into a set of DC voltages that can simultaneously drive each of the LED strings. However, since the load characteristics (current-voltage curve (IV Curve)) of each of the light-emitting diode strings are different, it is inferred that the current flowing through each of the light-emitting diode strings will be different ( That is, the current is unbalanced, which not only causes the brightness of the light source provided to the liquid crystal display panel of the light-emitting diode backlight module to be uneven, but also causes a problem of reducing the life of the light-emitting diode. In order to solve such a problem The current flowing through each of the LED strings can be adjusted by adding a Current Balance or Current Matching control line to the LED backlight module, thereby causing each of the LEDs to flow through each of the LEDs. The current of the polar body string can be the same (ie, current balance/match). A common current balancing or current matching control circuit can be composed of a current mirror circuit or a current feedback compensation circuit that is composed of a plurality of active components (such as MOSFETs). Alternatively, the current balancing or current matching control circuitry can be comprised of off-the-shelf current regulating wafers (e.g., current sink 1C). However, the number of adjustment channels of off-the-shelf current-regulating wafers is usually fixed (for example, usually 4 or 6 adjustment channels), since one adjustment channel is used to regulate the current flowing through a group of LED strings, When the light-emitting diode backlight module has, for example, 10 sets of light-emitting diode strings (the number of which is determined based on the size of different panels), three of them must have four 201212721

^HJ^6twf.d〇C/I adjustment channel (4) current adjustment M chip, or 2 current adjustment of the number of adjustment channel number of the current adjustment chip, but no matter which one you choose, there will be 2 unadjusted channel The situation arises, and this lack of cost will result in a surplus. [Summary of the Invention]

In view of the above, the present invention has a light-emitting diode-discriminating device capable of reducing current balance/electricity and melon matching characteristics, which solves the problems described in the foregoing, and includes: - power conversion a circuit for receiving and converting-converting a power source to generate a DC voltage to simultaneously drive a group of LEDs and a plurality of LEDs having a single-channel, respectively corresponding to the light-emitting diodes The body string, and the ith current-regulating B-plate is only used to regulate the flow through the ith group of LED strings, where i is a positive integer. The LED driving device proposed by the present invention mainly designs the current regulating wafer to have only a single regulating channel, thereby adjusting the current flowing through the single=light emitting diode string. Therefore, the regulation channels in each current regulating wafer can be considered as a precise current source. In addition, individual current regulating wafers can be connected together for expandable purposes. In this way, no matter how many sets of parallel LED strings are arranged in the LED backlight module, the number of which is determined based on the size of the different panels, as long as the same amount of the current regulating chip designed by the invention is matched. The current flowing through each of the light-emitting diode strings can be the same (ie, current balance/match), and there is no problem of excessive cost waste. S3 5 20121272 lJ〇c/l To make the above features and advantages of the present invention more comprehensible, the following specific embodiments are described in detail below with reference to the accompanying drawings. [Embodiment] Reference will now be made in detail to the exemplary embodiments embodiments In addition, wherever possible, the same reference numerals in the FIGS FIG. 1 is a schematic diagram of a light emitting diode driving device 10 according to an embodiment of the invention. Referring to FIG. 1, the LED driving device 10 of the present embodiment is at least suitable for driving a light emitting diode (LED) backlight module 20' of a liquid crystal display (LCD). Not limited to this. The LED backlight module 20 has a plurality of LED strings LLBi (i=l~m) arranged side by side, and each LED string LLBi (i=l~) m) is composed of a plurality of light-emitting diodes Li1 to LiN (i=l~m) connected in series, as shown in FIG. Further, the LED driving device 10 includes a power conversion circuit 101 and a plurality of current regulation chips 103_i (i = 1 m) having a single regulation channel. The power conversion circuit 101 is configured to receive and convert the input power source Vin to generate a DC voltage Vbus to simultaneously drive a plurality of parallel LED strings LLBi in the LED backlight module 20 (i=1) ~m) »

201212721 ^Tjjotwf.doc/I It is worth mentioning here that the power conversion circuit 101 is responsive to the type of input voltage Vin (such as DC or AC input voltage) and can be a DC-DC converter (when When the input voltage Vin is a direct current input voltage or an alternating current to direct current converter (AC-DC converter) (when the input voltage Vin is an alternating current input voltage), the present invention is not limited thereto. On the other hand, the current regulating wafers l〇3_i (i=i~m) correspond to the light emitting diode strings LLBi (i=l~m), respectively, and the i-th current regulating wafer l〇3_i (i=l~m) It is only used to regulate the current flowing through the ith group of LED strings LLBi (i=l~m). For example, the current regulating chip corresponds to the LED string LLB1; the current regulating chip 1〇3_2 corresponds to the LED string LLB2; and so on. In addition, the first current regulating wafer 103J is only used to regulate the current flowing through the first group of LED strings LLB1; the second current regulating wafer 1〇3_2 is only used to regulate the flow through the second group of LEDs. The current of the body string LLB2; and so on. More specifically, FIG. 3 is a schematic diagram showing an i-th current regulating wafer 103_i (i=l~m) according to an embodiment of the present invention. Referring to FIG. 1 to FIG. 3, in the embodiment, the i-th current clamp chip i〇3_i includes a controllable current source 301, a detection-control unit 303, The protection unit ( pr〇tecti〇n unit) 305, and the operation bias unit 307. First, it is worth mentioning that, in this embodiment, each current regulating chip 103 i (i= The controllable current source 301, the detection control unit 303, the protection unit 305, and the operating bias unit 307 in l~m) can be packaged to have five pins (for example, Pvcc, pGND, pLED,

201212721 ^HJJ〇LWl.d〇c/I

Pctr and Pdim) are integrated circuits (ic), but are not limited to this. Here, the first current regulating wafer 103_1 (i ==1) will be described as an example, and the other current regulating wafers 103_2 to 103_m (i = 2 to m) are deduced by analogy. In the first current regulating wafer 103_1, the controllable current source 301 is coupled between the first group of LEDs LLB1 and the ground GND through the pins Pled and Pgnd, and reacts to the dimming signal. DS provides a constant current source. In this embodiment, the controllable current source 301 is controlled by a dimming signal DS through the pin PDIM, and the dimming signal DS is used to adjust the first group of LED strings LLB1. The brightness, that is, the size of the constant current source provided by the controllable current source 301. The manner of adjusting the magnitude of the constant current source provided by the controllable current source 301 may be changing the voltage level of the dimming signal DS or changing the duty cycle of the dimming signal DS (duty CyCie). , but not limited to this β, the 'detection control unit _3 〇 3 will be coupled to the node between the controllable electric soul source 301 and the first group of light-emitting diodes LLB1 (n〇de) Ν Detecting the voltage drop of the controllable current source 301 (v〇ltage dr〇p/headr〇〇m), and controlling the power conversion by outputting the control power s VcrR (which can be a linear signal or a digital signal) through the connection _ peTR The magnitude of the DC voltage Vbus generated by the circuit 101 adjusts the voltage drop of the controllable current source 3〇1, thereby reducing the power loss generated by the controllable current source 301. In addition, the protection unit 3〇5 will also be lightly connected to the node N' to avoid the first current regulating wafer 103_1 201212721

j T J J 〇 i\vf.d〇c/I Damage caused by overvoltage, overpower, 〇ver temperature, or other factors. In addition, the 'operation biasing unit 307 is coupled to the controllable current source 301, the detection control unit 303, and the protection unit 〇5 for receiving an external supply voltage VCC through the pin pvcc, and according to The bias voltage (Visas) required for the operation of the controllable current source 301 and the reference voltage Vref required for the detection control unit 303 and the protection unit 305 to operate are provided. In the present embodiment, the pins Pdim of all the current regulating wafers 103_i (i = 1 m) can be directly coupled together. In this way, the controllable current source 301 in each current regulating chip 103_i (i=l~m) can be controlled by the same dimming signal DS, thereby synchronously adjusting each group of light emitting diodes. The brightness exhibited by the string LLBi (i=l~m). Of course, in other embodiments of the present invention, the controllable current source 301 in each of the current regulating wafers 103j (i=1~m) can also be controlled by the different dimming signals ds, thereby independently. / Respectively adjust the brightness of each set of LED strings LLBi (i = l ~ m): This method can achieve the use of regional dimming (l〇cal Dimming). Everything depends on the needs of the design. On the other hand, the pins PcTR of all current regulating wafers l〇3_i (i =: i~m) can also be directly connected together. In this way, the control voltage Vcm outputted by the detection control unit 3〇3 in each current regulating wafer 103j (i=i~m) is coupled to each other, so that the minimum control voltage Vctr can be Controlling the DC generated by the power conversion circuit 101

201212721 34338twt.doc/I The size of the voltage Vbus, that is, the minimum control voltage VCTR will take control of the power conversion circuit 101. It is worth mentioning that a sufficient voltage drop is required on the controllable current source 301 to maintain the controllable current tear 301 in each current regulating chip 103_i (i=l~m) as a constant current source (constant) Current source ). However, since the load characteristics of each group of LED strings LLBi (i=l~m) may be different, different LED strings LLBi. (i=l~m) correspond to each other. The voltage drop caused by the controllable current source 3〇1 will be different. Therefore, an excessive voltage drop will cause excessive power dissipation of the controllable current source 301, thereby reducing the efficiency of the controllable current source 301. The reason why the present embodiment particularly controls the power conversion circuit 101 using the minimum control voltage vCTR is to avoid a controllable current source in each current regulating wafer 10? 3〇1 produces excessive power waste. Therefore, as long as the DC voltage Vbus generated by the power conversion circuit 1〇1 allows the controllable current source 301 in each current regulating chip 1〇3-i (i=1~m) to have a sufficient voltage drop to maintain A constant current source can be used. Of course, in other embodiments of the present invention, the power conversion circuit 1〇1 may be controlled by the maximum control voltage vCTR or the average of all the control voltages vCTR depending on the application. Everything depends on the actual design needs. Similarly, all of the current regulating wafers 103-i (i=l~m) of the pins Pvcc can be directly coupled together, and all the current regulating wafers 1〇3" (1 = 1~m) of the pins PGND can also be Directly coupled together. As a result,

201212721 一... "Avf.doc/I The operating bias unit 3〇7 in each current regulating wafer 103j (i = 1~m) will receive the same external supply voltage ν (χ, so that all current regulating wafers The 103-i (i=i~m) architecture operates at the same operating voltage. It can be seen that each independent current regulating chip 1〇3—i (bm) can pass through the pin of phase f (IW, PGND). , PCTR and PDIM) are joined together to achieve the expandabie purpose (mechanism). In addition, although the above embodiment is to adjust the current of each chip 1〇3" (1-1 ~m) is an example of an integrated circuit having five pins, but the present invention is not limited thereto. In other words, if the light-emitting diode backlight module 10 does not need a dimming function, Then, the pin PmM of each current regulating wafer 103-i (i=l~m) can be omitted, so that the mother-current regulating chip 103-i becomes an integrated circuit with four pins. The design needs to be determined. In summary, the main body of the light-emitting diode driving device proposed by the present invention The current regulating chip is designed to have only a single regulation channel to regulate the current flowing through the single f:single LED string. In addition, each individual current regulating chip It can also be connected together to achieve the purpose of eXpandabie. In this way, no matter how many sets of LED strings are arranged in parallel in the LED backlight module, the number is based on the size of different panels. Decision), as long as the same number of current regulating wafers designed by the present invention are used, the current flowing through each of the light emitting diode strings can be the same (ie, current balance/current matching), and [ S 3; 201212721 and there is no problem of waste of unnecessary cost. Although the invention has been disclosed in the above embodiments, it is not intended to limit the invention, and any one of ordinary skill in the art without departing from the invention Within the spirit and scope, when some changes and refinements can be made, the scope of protection of the invention is defined by the scope of the patent application attached. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a view showing a 7F of a light-emitting diode driving device according to an embodiment of the present invention. FIG. 2 is a schematic diagram of a light-emitting diode string according to an embodiment of the present invention (i=l). FIG. 3 is a schematic diagram of an i-th current adjustment 曰 103—i (i=l~m) according to an embodiment of the present invention. [The main component symbol description] W: LED Body driving device 20: LED backlight module k 101: power conversion circuit 103-i (i=l~m): current regulating chip 301: controllable current source 303: detection control unit 3〇5: protection unit 307 : Working bias unit LLBi (i=i~m): LED string 201212721

^Hjjoiwf.doc/I

Lil~LiN (i=l~m): light-emitting diode

Pvcc, Pgnd, Pled, Pctr, Pdim: pin

Vin : Input power

Vbus : DC voltage VCC : External supply voltage GND : Ground potential

Vbias: bias

Vref: reference voltage

VcTR . Control voltage DS : Dimming signal N : Node

13

Claims (1)

201212721 VII. Patent application face: L A light-emitting diode driving device, comprising: a power conversion circuit for receiving and converting an input power source, thereby generating a DC voltage to simultaneously drive a plurality of parallel LED strings And a plurality of current regulating wafers having a single adjustment channel respectively corresponding to reading the LED strings' and the second current regulating chip is only responsible for regulating the current flowing through the ith group of LED strings, wherein Is a positive integer. 2. The light-emitting diode driving device according to the first aspect of the patent scope of the Shenqing patent, wherein the ith current-regulating chip comprises: a controllable current source coupled to the ith group of light-emitting diodes and a ground potential And providing a certain current in response to a dimming signal; a detecting control unit coupled to the node between the controllable current source and the second group of LEDs for detecting the controllable current The voltage drop of the source, and accordingly, the voltage of the DC voltage generated by the relay circuit is adjusted to adjust the voltage drop of the controllable current source; a protection unit coupled to the node for Avoiding the ith current regulation 曰B piece due to overvoltage, over power or overcurrent damage; and _, a working unit 'pure the controllable current source, the detection control list = and the protection unit' Receive-External Supply®, and to increase the bias voltage required for the operation of the 2-control current source, and to provide the reference voltage required for the detection to operate the protection unit early. The illuminating diode driving device of claim 2, wherein the controllable current source in each current regulating wafer is controlled by the same dimming signal, and The dimming signal is used to adjust the brightness of the LED strings. 4. The light-emitting diode driving device of claim 2, wherein the control voltages output by the detecting control unit in each current regulating chip are lightly combined with each other, thereby minimizing the control The voltage can control the magnitude of the DC voltage generated by the power conversion circuit. 5. The illuminating diode driving device of claim 2, wherein the operating bias unit in each current regulating wafer receives the same external supply voltage. 6. The illuminating diode driving device of claim 2, wherein the controllable current source in each current regulating chip, the detecting control unit, the protection arm, and the working bias unit are capable of It is packaged into an integrated circuit with multiple chats. 7. The illuminating diode driving device of claim 1, wherein the input power source is an AC input power source or a DC input power source. 8. The light-emitting diode driving device of claim 7, wherein when the input power source is the AC input power source, the power source is turned to SI 15 201212721 j^ouwi..d〇C/I circuit It is an AC-DC converter. 9. The LED driving device of claim 7, wherein when the input power source is the DC input power source, the power conversion circuit is a DC-DC converter. 10. The illuminating diode driving device of claim 1, wherein the illuminating diode driving device is at least adapted to drive a illuminating diode backlight module of a liquid crystal display. 16